Thermosetting composition

ABSTRACT

A thermosetting composition comprising (a) 97 to 40 percent by weight of at least one bis(dihydrobenzoxazine) prepared by the reaction of an unsubstituted or substituted bisphenol with at least one unsubstituted position ortho to each hydroxyl group, formaldehyde and a primary amine; and (b) 3 to 60 percent by weight of at least one bisphenol, wherein the percent by weight refer to the total amount of components (a) and (b), with the proviso that (a) and (b) add up to 100 percent by weight; and (c) optionally other components. Cured products made from these compositions have valuable chemical, physical and mechanical properties.

TECHNICAL FIELD

This invention relates to thermosetting compositions which comprise (a)97 to 40 percent by weight of one or more bis dihydrobenzoxazines on thebasis of bisphenols, (b) 3 to 60 percent by weight of at least onebisphenol, and (c) optionally a curing catalyst. The invention alsorelates to the use of this composition for the manufacture of anymaterials with a cured resin of this thermosetting composition.

BACKGROUND OF THE INVENTION

Benzoxazine compounds have been employed satisfactorily to produceprepregs, laminates, moulding material, RTM (resin transfer moulding)systems, sealants, sinter powders, cast articles, structural compositesparts, varnishes, surface coatings, electrical and electronic componentsby impregnating, coating, laminating or moulding processes. Such resinsare dimension stable and have good electrical and mechanical resistance,low shrinkage, low water absorption, medium to high glass transitiontemperatures and good retaining properties, in term of mechanicalproperties.

Benzoxazine compounds can easily be produced in several, well known waysby the reaction of bisphenols with a primary amine and formaldehyde,whereby the process can be carried out in the presence of solvents (seefor example U.S. Pat. No. 5,152,993 or U.S. Pat. No. 5,266,695) or inthe absence of solvents (see for example U.S. Pat. No. 5,543,516). Thecommon manufacture and various curing possibilities using hardeners suchas novolacs, polyepoxides or polyamines optionally together with acatalyst, or the catalytical and/or thermal curing as well as thevaluable properties of the resins make this class of thermosettingresins attractive.

EP 0 789 056 A2 describes a thermosetting resin composition withimproved curability comprising dihydrobenzoxazines of polyphenols suchas novolacs or bisphenol A and novolac phenolic resins. The compositionis used as adhesives or for the manufacture of moulded articles,coatings, sealings, prepregs for printed wiring boards and metal-cladlaminates with low water absorbance, improved none-flammability and highheat resistance. The use of polyhydroxy functional novolacs results insometimes undesirable high reactivities (low gel times) and in highercross-linked resins, which in general are more brittle.

WO 2006/035021 A1 describes bisbenzoxazines on the basis ofphenolphthalein for the preparation of polymers, which show a hightemperature stability and a good none-flammability. Polymerisation maybe carried out in presence of catalytic amounts of catalysts, such asthiodipropionic acid, phenols or sulfonyl diphenol. The use ofbisphenols as hardeners is not mentioned in WO 2006/035021 A1.

WO 00/27921 A1 discloses a ternary composition comprising 10 to 80weight percent of a benzoxazine monomer, 10 to 80 weight percent of anepoxy reactant and 1 to 80 weight percent of a phenolic resin orphenolic compound. The use of bisphenols as hardeners for thermosettingcompositions comprising bis(dihydrobenzoxazine) is not disclosed in WO00/27921 A1.

SUMMARY OF THE INVENTION

It has now been surprisingly found that bisphenols are excellenthardeners for the polymerization of bis(dihydrobenzoxazine) compoundswith improved reactivity and correspondingly lower gel times. It wasfurther found that the additional combination with catalytic amounts ofa protonic acid additionally increases the reactivity and furthersubstantially shortens the gel time. It was also found that acomposition comprising bis(dihydrobenzoxazine) compounds, bisphenols andoptionally a catalyst such as a protonic acid possess an unusual highlatency and storage stability regarding the increased reactivity. Theadmixed components can therefore be stored in one container and shippedto users, which is an economic advantage and much more comfortable forusers. Additionally, the processability and control during mouldingoperations such as pressing is improved by the reduction of flow throughthe higher reactivity, which results in improved dimensional accuracy.The incorporation of the mere difunctional bisphenols in the polymernetwork results in thermosetting polymers, which show high temperaturestability due to their unexpectedly high glass transition temperatures,good mechanical and also physical properties. Depending on the selectionof monomers, even a reduced combustibility can be achieved.

DETAILED DESCRIPTION OF THE INVENTION

A first object of the invention is a thermosetting compositioncomprising

(a) 97 to 40 percent by weight of at least one bis(dihydrobenzoxazine)prepared by the reaction of an unsubstituted or substituted bisphenolwith at least one unsubstituted position ortho to each hydroxyl group,formaldehyde and a primary amine; and(b) 3 to 60 percent by weight of at least one bisphenol selected fromhydrochinone, resorcinol, catechol, or from bisphenols of formula II,

whereinR₄ is hydrogen, dialkylamino; alkylthio; alkylsulfonyl; C₁-C₁₈alkyl;C₁-C₁₈alkoxy; C₁-C₁₈alkoxyalkyl; C₅-C₁₂cycloalkyl that is unsubstitutedor substituted by one or more C₁-C₆alkyl groups or C₁-C₆alkoxy groups;C₆-C₁₂aryl that is unsubstituted or substituted by one or moreC₁-C₆alkyl groups or C₁-C₆alkoxy groups; or C₇-C₁₃aralkyl that isunsubstituted or substituted by one or more C₁-C₆alkyl groups orC₁-C₆alkoxy groups;X₂ is a direct bond or a bivalent bridging group selected from —O—, —S—,—S(O)—, —S(O)₂—, —C(O)—, —NR₃—, —O—C(O)—, —O—C(O)—O—, —SO₂—O—,—O—SO₂—O—, —NR₃—C(O)—, —NR₃—C(O)—O—, —NR₃—C(O)—NR₃—, —NR₃SO₂—,—NR₃—SO₂—O—, —O—SO₂NR₃—, —NR₃SO₂—NR₃—, —P(O)(OR₃)O—, —OP(OR₃) O—,—(O)P(OR₃)—, —P(OR₃)—, —P(R₃)—, —O—(O)P(R₃)—O—, C₁-C₁₈alkylen,C₂-C₁₈alkyliden, C₃-C₁₂cycloalkyliden, —Si(OR₃)₂— and —Si(R₃)₂—; andR₃ is H or C₁-C₁₂alkyl, C₅- or C₆-cycloalkyl, C₅- orC₆-cycloalkyl-methyl or -ethyl, phenyl, benzyl or 1-phenyleth-2-yl,wherein the percent by weight refer to the total amount of components(a) and (b) with the proviso that (a) and (b) add up to 100%; and (c)optionally other components.

Preferably, the thermosetting composition additionally comprises

c) of a curing catalyst, preferably of a protonic acid curing catalyst.

In a preferred embodiment, the composition according to the inventioncomprises

(a) 95 to 50, preferably 95 to 60 and more preferably 94 to 70 percentby weight of at least one bis(dihydrobenzoxazine), and(b) 5 to 50, preferably 5 to 40 and more preferably 6 to 30 percent byweight of at least one bisphenol.

It was found that cured resins with a lower content of bisphenolspossess higher glass transition temperatures and thermostability,respectively Such a thermosetting compositions in addition have asufficiently high reactivity. Therefore, in a further preferredembodiment, the composition according to the invention comprises

(a) 97 to 75, preferably 96 to 80, more preferably 95 to 80 and mostpreferably 94 to 85 percent by weight of at least onebis(dihydrobenzoxazine); and(b) 3 to 25, preferably 4 to 20, more preferably 5 to 20 and mostpreferably 6 to 15 percent by weight of at least one bisphenol.

The composition according to the invention is cured at high temperaturessuch as above 130° C. Curing catalysts are useful therefore toaccelerate the curing process. These are preferably incorporated in lowlevels in order to avoid formation of volatile decomposition productswhich would effect the properties of the thermosetting plastics. Theamount of curing catalyst is preferably at most 5, further preferred0.001 to 4, more preferably 0.01 to 3, especially preferred 0.1 to 2 andin particular 0.1 to 1.5 percent by weight, based on the amount ofcomponents (a), and (b).

Curing catalysts, which accelerate the curing rate at a giventemperature are well known and may be selected from metal salts andmetal complexes, which may act as Lewis acids. Such salts and complexcompounds are described for example in EP-A-0 149 987 and include forexample iron(II)- or iron-(II)-chloride or -bromide, fluorides,chlorides and bromides of zinc, tin, zirconium, aluminium and boron,carboxylic acid salts of copper, cobalt, nickel, manganese, lead, zinc,tin and iron, carbonyls of nickel, iron, molybdenum and cobalt, andacetyl acetonates of iron, cobalt, nickel and cobalt. Some specificexamples are zinc octoate, dibutyltin diacetate, copper(II)-acetate, andzirconium dioctoate.

Preferred curing catalysts are protonic acids, especially aliphatic oraromatic mono- or polycarboxylic acids, sulfonic acids and phosphonicacids, having 1 to 20 and preferably 2 to 12 carbon atoms. The aliphaticand aromatic residues linking the carboxylic groups may contain heteroatoms and groups such as O, S, —N═, —NH— and —N(C₁-C₄alkyl)-. Thealiphatic and aromatic residues may be unsubstituted or substituted withone or more C₁-C₆alkyl, C₁-C₆hydroxyalkyl or C₁-C₆alkoxy groups, halogen(F or Cl), hydroxyl or amino. Preferred substituents are C₁-C₄alkyl,C₁-C₄hydroxyalkyl or C₁-C₄alkoxy groups, F or Cl. The carboxylic acidmay contain preferably 1 to 4 and more preferably 1 or 2 carboxylicgroups. The aliphatic or aromatic residue can be selected from alkanes,alkenes, cycloalkanes, heterocycloalkanes, cycloalkenes,heterocycloalkenes, carbocyclic or heterocyclic aromates, such asC₁-C₁₈alkyl, C₁-C₁₈alkenyl, C₃-C₁₂cycloalkyl, C₃-C₁₂heterocycloalkyl,C₆-C₁₈aryl, C₆-C₁₈heteroaryl. A preferred group of carboxylic acids isselected from those of formulae X₂—C_(n)H_(2n)—COOH andX₂—C₆-C₁₀arylen-COOH, wherein X₂ is hydrogen or the group —COOH, and nis a number of 1 to 12, preferably 1 to 6.

Some preferred examples for carboxylic acids are acetic acid, propanoicacid, butanoic acid, octanoic acid, dodecanoic acid, octanoic acid,maleic acid, succinic acid, nonyl- or dodecyl-succinic acid, glutaricacid, adipic acid, pimelic acid, suberic acid, azelaic acid, benzoicacid, phthalic acid, isophthalic acid, terephthalic acid and naphthalenedicarboxylic acid. Other examples are methyl sulfonic acid,trifluoromethyl sulfonic acid, phenyl sulfonic acid, toluoyl sulfonicacid, methyl phosphonic acid and phenyl phosphonic acid.

An especially preferred curing catalyst is adipic acid.

Bis(dihydrobenzoxazines) on the basis of bisphenols are well known,commercially available and can be prepared according to well known andpublished methods. Bis(dihydrobenzoxazines) on the basis of bisphenolsmay correspond to formula I,

whereinR₁ is C₁-C₁₈alkyl, or C₃-C₁₂cycloalkyl, C₃-C₁₂cycloalkyl-C₁-C₄alkyl,C₆-C₁₈aryl or C₆-C₁₈aryl-C₁-C₄alkyl, which are unsubstituted orsubstituted by one or more C₁-C₆alkyl groups or C₁-C₆alkoxy groups;R₂ hydrogen, dialkylamino; alkylthio; alkylsulfonyl; C₁-C₁₈alkyl;C₁-C₁₈alkoxy; C₁-C₁₈alkoxyalkyl; C₅-C₁₂cycloalkyl that is unsubstitutedor substituted by one or more C₁-C₆alkyl groups or C₁-C₆alkoxy groups;C₆-C₁₂aryl that is unsubstituted or substituted by one or moreC₁-C₆alkyl groups or C₁-C₆alkoxy groups; or C₇-C₁₃aralkyl that isunsubstituted or substituted by one or more C₁-C₆alkyl groups orC₁-C₆alkoxy groups;X₁ is a direct bond or a bivalent bridging group selected from —O—, —S—,—S(O)—, —S(O)₂—, —C(O)—, —NR₃—, —O—C(O)—, —O—C(O)—O—, —SO₂—O—,—O—SO₂—O—, —NR₃—C(O)—, —NR₃—C(O)—O—, —NR₃—C(O)—NR₃—, —NR₃SO₂—,—NR₃—SO₂—O—, —O—SO₂NR₃—, —NR₃SO₂—NR₃—, —P(O)(OR₃)O—, —OP(OR₃)O—,—(O)P(OR₃)—, —P(OR₃)—, —P(R₃)—, —O—(O)P(R₃)—O—, C₁-C₁₈alkylen,C₂-C₁₈alkyliden, C₃-C₁₂cycloalkylen or -cycloalkyliden, —Si(OR₃)₂— and—Si(R₃)₂—; andR₃ is H or C₁-C₁₂alkyl, C₅- or C₆-cycloalkyl, C₅- orC₆-cycloalkyl-methyl or -ethyl, phenyl, benzyl or 1-phenyleth-2-yl.

When the radicals R₁ to R₃ are alkyl, alkoxy or alkoxyalkyl, thosealkoyl or alkoxy radicals can be straight-chained or branched and maycontain 1 to 12, more preferably 1 to 8 and most preferably 1 to 4 Catoms.

Examples of alkyl groups are methyl, ethyl, isopropyl, n-propyl,n-butyl, isobutyl, sec-butyl, tert-butyl and the various isomericpentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl,tetradecyl, pentadecyl, hexadecyl, heptadecyl and octadecyl groups.

Suitable alkoxy groups are, for example, methoxy, ethoxy, isopropoxy,n-propoxy, n-butoxy, isobutoxy, sec-butoxy, tert-butoxy and the variousisomeric pentyloxy, hexyloxy, heptyloxy, octyloxy, nonyloxy, decyloxy,undecyloxy, dodecyloxy, tridecyloxy, tetradecyloxy, pentadecyloxy,hexadecyloxy, heptadecyloxy and octadecyloxy groups.

Examples of alkoxyalkyl groups are 2-methoxyethyl, 2-ethoxyethyl,2-methoxypropyl, 3-methoxypropyl, 4-methoxybutyl and 4-ethoxybutyl.

Cycloalkyl is preferably C₅-C₈cycloalkyl, especially C₅- orC₆-cycloalkyl. Some examples thereof are cyclopentyl, methylcyclopentyl,cyclohexyl, cycloheptyl and cyclooctyl.

Aryl groups are, for example, phenyl, naphthyl and anthryl.

Aralkyl preferably contains from 7 to 12 carbon atoms and especiallyfrom 7 to 11 carbon atoms. It may be, for example, benzyl, phenethyl,3-phenylpropyl, α-methylbenzyl, 4-phenylbutyl or α,α-dimethylbenzyl.

R₁ is preferably C₁-C₁₂alkyl, C₅-C₈cycloalkyl orC₅-C₈cycloalkyl-C₁-C₂alkyl that is unsubstituted or substituted by oneor more C₁-C₄alkyl groups or C₁-C₄alkoxy groups, C₆-C₁₀aryl orC₆-C₁₀aryl-C₁-C₂alkyl that is unsubstituted or substituted by one ormore C₁-C₄alkyl groups or C₁-C₄alkoxy groups.

In a more preferred embodiment of the present invention, R₁ isC₁-C₆alkyl, or phenyl or benzyl—both unsubstituted or substituted by oneor more methyl groups or methoxy groups.

According to the invention, compounds of formula I are preferred, inwhich R₁ is isopropyl, iso- or tertiary-butyl, n-pentyl or phenyl.

R₂ in the compounds of formula I is preferably hydrogen.

Cycloalkylen X₁ may be a polycycloalkylen having 2 to 4 condensed and/orbridged carbon cycles such as bicyclo-[2,2,1]-heptanylene ortricyclo-[2,1,0]-decanylene.

X₁ is preferably a direct bond or more preferably a bivalent bridginggroup selected from —O—, —S—, —S(O)—, —S(O)₂—, —C(O)—, —P(O)(OR₃)O—,—OP(OR₃)O—, —OP(OR₃)—, —P(OR₃)—, —P(R₃)—, C₁-C₂-alkylen, andC₁-C₁₂alkyliden, wherein R₃ C₁-C₄alkyl, C₅- or C₆-cycloalkyl, phenyl orbenzyl.

It was found that S and P containing bridging groups improveflammability resistance and these groups may be selected if saidresistance is desired.

R₃ is preferably H, C₁-C₁₂alkyl, C₅- or C₆-cycloalkyl, C₅- orC₆-cycloalkyl-methyl or -ethyl, phenyl, benzyl or 1-phenyleth-2-yl. IfR₃ is part of the groups P(O)(OR₃)O—, —OP(OR₃)O—, —OP(OR₃)—, —P(OR₃)—and —P(R₃), then it is preferably not hydrogen.

In a preferred embodiment, R₃ is selected from C₁-C₄alkyl, cyclohexyl,phenyl or benzyl.

Some preferred examples of bisphenols used to preparebis(dihydrobenzoxazines) are 4,4′-dihydroxybiphenyl,(4-hydroxyphenyl)₂C(O) (DHBP), bi(4-hydroxyphenyl)ether,bi(4-hydroxyphenyl)thioether, bisphenol A, bisphenol AP, bisphenol E,bisphenol H, bisphenol F, bisphenol S, bisphenol Z, phenolphthalein andbi(4-hydroxyphenyl)tricyclo-[2,1,0]-decan.

The bisphenol component (b) may be selected from hydrochinone,resorcinol, catechol, or from bisphenols of formula II,

whereinR₄ is hydrogen, dialkylamino; alkylthio; alkylsulfonyl; C₁-C₁₈alkyl;C₁-C₁₈alkoxy; C₁-C₁₈alkoxyalkyl; C₅-C₁₂cycloalkyl that is unsubstitutedor substituted by one or more C₁-C₆alkyl groups or C₁-C₆alkoxy groups;C₆-C₁₂aryl that is unsubstituted or substituted by one or moreC₁-C₆alkyl groups or C₁-C₆alkoxy groups; or C₇-C₁₃aralkyl that isunsubstituted or -substituted by one or more C₁-C₆alkyl groups orC₁-C₆alkoxy groups;X₂ is a direct bond or a bivalent bridging group selected from —O—, —S—,—S(O)—, —S(O)₂—, —C(O)—, —NR₃—, —O—C(O)—, —O—C(O)—O—, —SO₂—O—,—O—SO₂—O—, —NR₃—C(O)—, —NR₃—C(O)—O—, —NR₃—C(O)—NR₃—, —NR₃SO₂—,—NR₃—SO₂—O—, —O—SO₂NR₃—, —NR₃SO₂—NR₃—, —P(O)(OR₃)O—, —OP(OR₃)O—,—(O)P(OR₃)—, —P(OR₃)—, —P(R₃)—, —O—(O)P(R₃)—O—, C₁-C₁₈alkylen,C₂-C₁₈alkyliden, C₃-C₁₂cycloalkyliden, —Si(OR₃)₂— and —Si(R₃)₂—; andR₃ is H or C₁-C₁₂alkyl, C₅- or C₆-cycloalkyl, C₅- orC₆-cycloalkyl-methyl or -ethyl, phenyl, benzyl or 1-phenyleth-2-yl.

R₃ in formula II may independently have the same preferred meanings asR₃ in formula I.

R₄ in formula II may independently have the same preferred meanings asR₂ in formula I. R₄ is in particular hydrogen or C₁-C₄alkyl, such asmethyl or ethyl

X₂ preferably is a direct bond or a bivalent bridging group selectedfrom —O—, —S—, —S(O)₂—, —C(O)—, —NR₃, C₁-C₄alkylen (for examplemethylene or 1,2-ethylene), C₂-C₆alkyliden (for example ethylidene, 1,1-or 2,2-propylidene, 1,1- or 2,2-butylidene, 1,1-, 2,2- or3,3-pentylidene, or 1,1-, 2,2- or 3,3-hexylidene) or C₅-C₈cycloalkyliden(cyclopentylidene, cyclohexylidene or cyclooctylidene), whereby R₃ ispreferably hydrogen or C₁-C₄alkyl.

If an improved flammability resistance is desired, X₂ is a bivalentbridging group selected from —S—, and —S(O)₂—.

Preferred bisphenols of formula II are 4,4′dihydroxy-biphenyl,(4-hydroxyphenyl)₂C(O) (DHBP), bi(4-hydroxyphenyl)ether,bi(4-hydroxyphenyl)thioether, bisphenol A, bisphenol AP, bisphenol E,bisphenol H, bisphenol F, bisphenol S and bisphenol Z. Bisphenols withsulfur containing bridging groups may be selected if improvement of highflammability resistance is desired.

The properties of the thermosetting resins can be tailored for certainapplications by addition of usual additives. The following additives areof particular importance:

reinforcement fibers, such as glass, quartz, carbon, mineral andsynthetic fibers (Keflar, Nomex), natural fibres, such as flax, jute,sisal, hemp in the usual forms of short fibers, staple fibers, threads,fabrics or mats;plasticizers, especially phosphorus compounds;mineral fillers, such as oxides, carbides, nitrides, silicates andsalts, e.g. quartz powder, fused silica, aluminium oxide, glass powder,mica, kaolin, dolomite, carbon black or graphite;pigments and dyestuffs;micro hollow spheres;metal powders;flame retardants;defoaming agents;slip agents;thixotropes;adhesion promoters; andmould release agents.

It was also surprisingly found that the presence of aromatic polyamines,e.g. bisphenyldiamines such as 4,4′-diaminodiphenylsulfone or methylenebisaniline, in the thermosetting resin composition improves the adhesionof the cured resin to metallic surfaces, such as copper surfaces.Therefore, in a further preferred embodiment of the invention, aromaticpolyamines are present. The amount of these may range from 0.01 to 5percent by weight, preferably 0.1 to 3 percent by weight, and especiallypreferred 0.5 to 2 percent by weight, based on the total amount ofcomponents (a) and (b). Preferably, 4,4′-diaminodiphenylsulfone is used.

The thermosetting composition according to the invention can alsocomprise a solvent or a solvent mixture, especially when it is used aslaminating or surface coating composition. Examples of solvents that areparticularly suitable include methylethylketone, acetone,N-methyl-2-pyrrolidone, N,N-dimethyl formamide, pentanol, butanol,dioxolane, isopropanol, methoxy propanol, methoxy propanol acetate,dimethylformamide, glycols, glycol acetates and toluene, xylene. Theketones and the glycols are especially preferred. Typically, thelaminating composition will contain 20 to 30% by weight, preferably 30%by weight, of a solvent.

The thermosetting composition according to the invention can be cured orpre-cured at temperatures of about 130 to 240° C., preferably 150 to220° C. and in particular 160 to 200° C. for the manufacture ofprepregs, laminates or hot melting moulding processes.

The thermosetting composition according to the invention can be used forexample for the manufacture of composites from prepregs or B stageresins, and RTM (resin transfer moulding) systems.

The thermosetting compositions according to the invention can be used,for example, as solvent-free casting resins, surface coating resins,laminating resins, moulding resins, potting resins, encapsulating resinsand adhesives to produce moulded or coated articles or composites forthe electrical and electronic industry, in the automotive and aerospaceindustry, or for surface protection of many articles, e.g. pipes andpipelines.

Curing of the composition and an impregnation and lamination process isexplained in the following:

(1) A benzoxazin-containing formulation is applied to or impregnatedinto a substrate by rolling, dipping, spraying, other known techniquesand/or combinations thereof. The substrate is typically a woven ornonwoven fiber mat containing, for instance, glass fibers, carbon ormineral fibers or paper.(2) The impregnated substrate is “B-staged” by heating at a temperaturesufficient to evaporate solvent (if the latter is present) in thebenzoxazin formulation and to partially cure the benzoxazin formulation,so that the impregnated substrate can be handled easily. The “B-staging”step is usually carried out at a temperature of from 80° C. to 220° C.and for a time of from 1 minute to 15 minutes. The impregnated substratethat results from “B-staging” is called a “prepreg”. The temperature ismost commonly 100° C. for composites and 130° C. to 200° C. forelectrical laminates.(3) One or more sheets of prepreg are stacked on top of each other ormay alternate with one or more sheets of a conductive material, such ascopper foil, if an electrical laminate is desired.(4) The laid-up sheets are pressed at high temperature and pressure fora time sufficient to cure the resin and form a laminate. The temperatureof this lamination step is usually between 100° C. and 240° C., and ismost often between 165° C. and 190° C. The lamination step may also becarried out in two or more stages, such as a first stage between 100° C.and 150° C. and a second stage at between 165° C. and 190° C. Thepressure is usually from 50 N/cm² and 500 N/cm². The lamination step isusually carried out for a time of from 1 minute to 200 minutes, and mostoften for 45 minutes to 90 minutes. The lamination step may optionallybe carried out at higher temperatures for shorter times (such as incontinuous lamination processes) or for longer times at lowertemperatures (such as in low energy press processes).(5) Optionally, the resulting laminate, for example, a copper-cladlaminate, may be post-treated by heating for a time at high temperatureand ambient pressure. The temperature of post-treatment is usuallybetween 120° C. and 250° C. The post-treatment time usually is between30 minutes and 12 hours.

Solid substrates for coating purposes may be selected from metal, metalalloys, wood, glass, minerals such as silicates, corundum or boronnitride, and plastics.

The cured resins possess a high chemical resistance, corrosionresistance, mechanical resistance, durability, hardness, toughness,flexibility, temperature resistance or stability (high glass transitiontemperatures), reduced combustibility, adhesion to substrates andde-lamination resistance.

Another object of the invention relates to the use of the thermosettingcomposition according to the invention for the manufacture of mouldedarticles, surface coatings, composites and laminates.

A further object of the invention are cured products manufactured fromthe thermosetting composition according to the invention.

EXAMPLES

The following examples explain the invention.

A) Preparation of Thermosetting Compositions Example A1 to 10

A solid mixture of (in parts by weight) component (a) benzoxazine,component (b) bisphenol and optionally curing catalyst (c) is molten at130-140° C. under thorough stirring. The gel time of such homogenousmixture is measured on a hot plate at 180° C. The gel time has beendetermined according to the standard test method IPC-TM-650-2.3.18,however, the measurement has been carried out on a hot plate of 180° C.instead of 171° C. The mixture is cured in an oven at 200° C. for 90minutes. The onset temperature (onset T), temperature peak (T peak),enthalpie and glass transition temperature (Tg) has been determined on aDSC machine of Mettler type DSC 823 (condition: from 30 to 350° C.,heating rate 20° C./min).

The results are given in the following Tables 1 and 2.

TABLE 1 A1 A2 A3 A4 A5 A6 bisphenol F benzoxazine 10 10 10 10phenolphthalein 10 benzoxazine bisphenol A benzoxazine 104,4′-dihydroxy- 1 1 1 0.4 0.4 1.2 diphenylsulfone bisphenol A adipicacid 0.56 benzoic acid gel time/180° C. (sec) 455 323 430 1140 148 317DSC 30-350° C., 20° C./min onset T (° C.) 195 192 204 220 176 188 T peak(° C.) 226 229 233 240 208 215 enthalpie (J/g) 243 171 224 228 225 243T_(g) after 90 min/200° C. 185 215 179 169 183 179

TABLE 2 A7 A8 A9 A10 C1 C2 bisphenol F benzoxazine 10 10 10 10phenolphthalein 10 benzoxazine bisphenol A benzoxazine 104,4′-dihydroxy- 1.2 0.4 diphenylsulfone bisphenol A 0.40 2phenol-formaldehyde 1 novolac^(a) adipic acid 0.1 benzoic acid 0.1 geltime/180° C. (sec) 250 311 973 511 2040 720 DSC 30-350° C., 20° C./minonset (° C.) 185 186 218 192 240 196 T peak (° C.) 212 208 236 218 254236 enthalpy (J/g) 254 267 274 272 290 204 T_(g) after 90 min/200° C.185 162 163 157 ^(a)= DURITE ® SD-1702 ex Borden Chemical, Inc.;viscosity at 150° C.: 1400-2400 cps; Mw: 2500; Mn: 600Remarks: The examples (A1 to A10) according to the invention summarizedin Tables 1 and 2 demonstrate enhanced reaction (shorter gel times) whena protonic acid catalyst is used in addition (A5 and A7). Unusual highglass transition temperatures result, especially when dicarboxylic acidssuch as adipic acid are used as catalysts.

The benzoxazines used correspond to formula

wherein X₁ is —CH₂— (bisphenol F benzoxazine), 2,2-propylidene(bisphenol A benzoxazine) or 1(3H)-isobenzofuranone-3,3′-ylidene.

C1 and C2 are comparative examples. The comparison of C2 with A2 clearlydemonstrate a lower gel time and a higher reactivity (lower T peak) forexample A2 according to the invention relative to comparative exampleC2.

1. A thermosetting composition comprising: (a) 97 to 40 percent byweight of at least one bis(dihydrobenzoxazine) prepared by the reactionof an unsubstituted or substituted bisphenol with at least oneunsubstituted position ortho to each hydroxyl group, Formaldehyde and aprimary amine; and (b) 3 to 60 percent by weight of at least onebisphenol selected from hydrochinone, resorcinol, catechol, andbisphenols of formula II,

wherein R₄ is hydrogen, dialkylamino; alkylthio; alkylsulfonyl; C₁-C₁₈alkyl; C₁-C₁₈ alkoxy; C₁-C₁₈alkoxyalkyl; C₅-C₁₂ cycloalkyl that isunsubstituted or substituted by one or more C₁-C₆ alkyl groups or C₁-C₆alkoxy groups; C₆-C₁₂ aryl that is unsubstituted or substituted by oneor more C₁-C₆ alkyl groups or C₁-C₆ alkoxy groups; or C₇-C₁₃ aralkylthat is unsubstituted or substituted by one or more C₁-C₆ alkyl groupsor C₁-C₆ alkoxy groups; X₂ is a direct bond or a bivalent bridging groupselected from —O—, —S—, —S(O)—, —S(O)₂—, —C(O)—, —NR₃—, —O—C(O)—,—O—C(O)—O—, —SO₂—O—, —O—SO₂—O—, —NR₃—C(O)—, —NR₃—C(O)—O—,—NR₃—C(O)—NR₃—, —NR₃SO₂—, —NR₃—SO₂—O—, —O—SO₂NR₃—, —NR₃SO₂—NR₃—,—P(O)(OR₃)O—, —OP(OR₃)O—, —(O)P(OR₃)—, —P(OR₃)—, —P(R₃)—,—O—(O)P(R₃)—O—, C₁-C₁₈ alkylen, C₂-C₁₈ alkyliden, C₃-C₁₂ cycloalkyliden,—Si(OR₃)₂— and —Si(R₃)₂—; and R₃ is H or C₁-C₁₂ alkyl, C₅- orC₆-cycloalkyl, C₅- or C₆-cycloalkyl-methyl or -ethyl, phenyl, benzyl or1-phenyleth-2-yl wherein the percent by weight refers to the totalamount of components (a) and (b), with the proviso that (a) and (b) addup to 100 percent by weight; and (c) optionally other components.
 2. Athermosetting composition according to claim 1, comprising additionallyc) a curing catalyst.
 3. A thermosetting composition according to claim2, wherein the catalyst is a proton acid curing catalyst.
 4. Athermosetting composition according to claim 1, which comprises: (a) 95to 50 percent by weight of at least one bis(dihydrobenzoxazine), and (b)5 to 50 percent by weight of at least one bisphenol.
 5. A thermosettingcomposition according to claim 1, which comprises (a) 97 to 75 percentby weight of at least one bis(dihydrobenzoxazine); and (b) 3 to 25percent by weight of at least one bisphenol.
 6. A thermosettingcomposition according to claim 1, which comprises as component (a)bis(dihydrobenzoxazines) of formula I,

wherein R₁ is C₁-C₁₈ alkyl, or C₃-C₁₂ cycloalkyl, C₃-C₁₂cycloalkyl-C₁-C₄ alkyl, C₆-C₁₈ aryl or C₆-C₁₈ aryl-C₁-C₄ alkyl, whichare unsubstituted or substituted by one or more C₁-C₆ alkyl groups orC₁-C₆ alkoxy groups; R₂ is hydrogen, dialkylamino; alkylthio;alkylsulfonyl; C₁-C₁₈ alkyl; C₁-C₁₈ alkoxy; C₁-C₁₈ alkoxyalkyl; C₅-C₁₂cycloalkyl that is unsubstituted or substituted by one or more C₁-C₆alkyl groups or C₁-C₆ alkoxy groups; C₆-C₁₂ aryl that is unsubstitutedor substituted by one or more C₁-C₆ alkyl groups or C₁-C₆ alkoxy groups;or C₇-C₁₃ aralkyl that is unsubstituted or substituted by one or moreC₁-C₆ alkyl groups or C₁-C₆ alkoxy groups; X₁ is a direct bond or abivalent bridging group selected from —O—, —S—, —S(O)—, —S(O)₂—, —C(O)—,—NR₃—, —O—C(O)—, —O—C(O)—O—, —SO₂—O—, —O—SO₂—O—, —NR₃—C(O)—,—NR₃—C(O)—O—, —NR₃—C(O)—NR₃—, —NR₃SO₂—, —NR₃—SO₂—O—, —O—SO₂NR₃—,—NR₃SO₂—NR₃—, —P(O)(OR₃)O—, —OP(OR₃)O—, —(O)P(OR₃)—, —P(OR₃)—, —P(R₃)—,—O—(O)P(R₃)—O—, C₁-C₁₈ alkylen, C₂-C₁₈ alkyliden, C₃-C₁₂ cycloalkyliden,—Si(OR₃)₂— and —Si(R₃)₂—; and R₃ is H or C₁-C₁₂ alkyl, C₅- orC₆-cycloalkyl, C₅- or C₆-cycloalkyl-methyl or -ethyl, phenyl, benzyl or1-phenyleth-2-yl.
 7. A thermosetting composition according to claim 6,wherein R₁ is C₁-C₆ alkyl, or phenyl or benzyl that is unsubstituted orsubstituted by one or more methyl groups or methoxy groups.
 8. Athermosetting composition according to claim 6, wherein R₂ in thecompound of formula I is hydrogen.
 9. A thermosetting compositionaccording to claim 6, wherein X₁ is a direct bond or a bivalent bridginggroup selected from —O—, —S—, —S(O)—, —S(O)₂—, —C(O)—, —P(O)(OR₃)O—,—OP(OR₃)O—, —OP(OR₃)—, —P(OR₃)—, —P(R₃)—, C₁-C₂ alkylen, and C₁-C₁₂alkyliden, and wherein R₃ is C₁-C₄ alkyl, C₅- or C₆-cycloalkyl, phenylor benzyl.
 10. A thermosetting composition according to claim 6, whereinR₃ is H, C₁-C₁₂ alkyl, C₅- or C₆-cycloalkyl, C₅- or C₆-cycloalkyl-methylor -ethyl, phenyl, benzyl or 1-phenyleth-2-yl, with the proviso that ifR₃ is in the groups —P(O)(OR₃)O—, —OP(OR₃)O—, —OP(OR₃)—, —P(OR₃)— and—P(R₃)— then it is not hydrogen.
 11. A thermosetting compositionaccording to claim 1, wherein in formula (II) R₄ is hydrogen or C₁-C₄alkyl.
 12. A thermosetting composition according to claim 1, wherein informula (II) X₂ is a direct bond or a bivalent bridging group selectedfrom —O—, —S—, —S(O)₂—, —C(O)—, —NR₃, C₁-C₄ alkylen, C₂-C₆ alkyliden andC₅-C₈ cycloalkyliden, and wherein R₃ is hydrogen or C₁-C₄ alkyl.
 13. Athermosetting composition according to claim 1, wherein in formula (II)X₂ is a bivalent bridging group selected from —S—, and —S(O)₂—.
 14. Athermosetting composition according to claim 1, which additionallycomprises an aromatic polyamine.
 15. A thermosetting compositionaccording to claim 2, wherein the curing catalyst is adipic acid. 16.(canceled)
 17. (canceled)
 18. A method of forming a laminate comprising:(a) applying the thermosetting composition of claim 1 to a substrate;(b) heating the substrate to partially cure the thermosettingcomposition and form a prepeg; (c) optionally repeating steps (a) and(b); (d) stacking one or more sheets of prepeg on top of each other; and(e) pressing the stacked sheets at a temperature of between 100° C. to240° C. and a pressure of between 50 N/cm² to 500 N/cm² to form thelaminate.
 19. The method of claim 18, wherein the substrate is a wovenor nonwoven fiber mat.
 20. A method of coating a substrate comprisingapplying the thermosetting composition of claim 1 to the surface of thesubstrate.
 21. The method of claim 20, wherein the substrate is a metal,a metal alloy, wood, glass, a mineral or plastic.
 22. A cured productproduced by curing the thermosetting composition of claim 1.